TextEditor: Modernize

override, auto, nullptr, member initializers.

Change-Id: I04c6ebb683849568973bd7782fb5a3279267141e
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/texteditor/snippets/snippet.cpp

@@ -222,7 +222,7 @@ Snippet::ParsedSnippet Snippet::parse(const QString &snippet)
             } else {
                 int length = result.text.count() - start;
                 result.ranges << ParsedSnippet::Range(start, length, mangler);
-                mangler = 0;
+                mangler = nullptr;
                 start = -1;
             }
             continue;